/Engine/Source/Editor/UnrealEd/Public/Commandlets/AssetRegistryGenerator.h
Computes just the list of packages in the PreviousState that no longer exist in the current state.
void ComputePackageRemovals ( const [FAssetRegistryState](API\Runtime\AssetRegistry\AssetRegistry\FAssetRegistryState) & PreviousState, [TArray](API\Runtime\Core\Containers\TArray)< [FName](API\Runtime\Core\UObject\FName) > & OutRemovedPackages, [TMap](API\Runtime\Core\Containers\TMap)< [FName](API\Runtime\Core\UObject\FName), [FGeneratorPackageInfo](API\Editor\UnrealEd\Commandlets\FAssetRegistryGenerator\FGeneratorPackageInfo) > & OutGeneratorPackages, int32 & OutNumNeverCookPlaceHolderPackages )